Just a question others will ask... Are you going to charge their card right away? More importantly how is your store setup to handle credit cards? Only after fulfilment? You need to ensure that you properly manage this with the charges, and watch the automatic notifications that go out.
In most cases I recommend a "let us know it is ready to order" email form that will send an email to the store owner email address. When it is ready you send them a nice email with a link to the product reminding them to pay.
we have done the "enquire for price" in a lot of different ways. The best way is a custom lightbox style form that pops up and ensures that the product details (sku, title, etc) is added to the email content so you know what product they are asking about - see http://www.hotandmightydirect.com/products/trailer-mounted-pressure-washer-chopper-a1-mec-3005
If you are intested we can help out... just send me a mail at trevor at carlowseo.com